Anonymous

If one is the captain, s/he would sail a boat, but a passenger would sail on a boat.

Anonymous

They are both correct, but while both of them mean you enjoy being on a boat and sailing, the first one has the specific meaning that you enjoy 'driving' the boat: being in charge, operating, controlling, holding the wheel.

Anonymous

I like Sailing... is fine. If you are sailing, it is already assumed you are on a boat.